Image prediction encoding device, image prediction decoding device, image prediction encoding method, image prediction decoding method, image prediction encoding program, and image prediction decoding program

ABSTRACT

The image predictive encoding device  10  comprises an intra frame predictive signal generation method determination section  15  which determines, for adjacent areas comprising regenerated pixel signals and adjacent to the target area, a predictive method which is derived on the basis of data corresponding to the adjacent areas as an R mode predictive method or an L mode predictive method, an intra frame predictive signal generation section  16  which generates an intra frame predictive signal on the basis of the R mode predictive method thus determined, and a subtractor  18 , a transform section  19 , a quantization section  20 , and an entropy encoding section  25  which encode a residual signal of a pixel signal of the target area on the basis of the generated intra frame predictive signal.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/825,649, filed on Nov. 29, 2017, which is a continuation of U.S.application Ser. No. 15/385,358, filed on Dec. 20, 2016 (now U.S. Pat.No. 9,860,534), which is a continuation of U.S. application Ser. No.14/100,740, filed on Dec. 9, 2013, (now U.S. Pat. No. 9,571,831), whichis a continuation of U.S. application Ser. No. 12/090,715 (nowabandoned), filed on Aug. 6, 2008, which is a National Stage ofPCT/JP2006/320766, filed on Oct. 18, 2006, and claims the benefit ofpriority under 35 U.S.C. § 119 of Japanese Application No. 2005-304534,filed on Oct. 19, 2005. The entire contents of each of the above areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an image prediction encoding device, animage prediction decoding device, an image prediction encoding method,an image prediction decoding method, an image prediction encodingprogram, and an image prediction decoding program.

BACKGROUND ART

Compression is conventionally carried out by using compression encodingtechnology to compress image data in order to efficiently transmit andstore still image data and moving image data and so forth. The MPEG1 toMPEG4 and H.261 to H.264 systems and so forth are widely used as suchcompression encoding technology for moving images.

With such encoding systems, encoding processing and decoding processingare carried out after dividing image data constituting the encodingtarget into a plurality of blocks. Furthermore, in the case of the MPEG4and H.264 systems, when encoding a target block of an intra frame inorder to further raise the encoding efficiency, a predictive signal isgenerated by using regenerated pixel signals which are adjacent to thetarget block on the same frame. The regenerated pixel signals are thepixel signals that have been reconstructed from previously compressedpixel data. Furthermore, a differential signal which is obtained bysubtracting the predictive signal from the pixel signal of the targetblock is encoded.

Here, in MPEG4, the pixel signal of the target block is subjected topredictive encoding after performing a discrete cosine transform on thepixel signal of the target block. In other words, for the DC componentcoefficient of the target block and the AC component coefficient of thefirst row or first column of the target block, a coefficient for thecorresponding component of the block above or to the left of the targetblock is taken as the predictive value and the difference between theboth values is encoded. The determination of the predictive values iscarried out on the basis of the size of the gradient of the DCcomponents of a block diagonally above the target block and a blockabove the target block or to the left thereof. Such an intra framepredictive method appears in Patent Document 1 below.

However, with H.264, a method of generating a predictive signal byextrapolating regenerated pixel values which are adjacent to the targetblock in a predetermined direction is adopted. The generation of anintra frame predictive signal in this pixel domain has the advantage ofmaking it possible to predict the details in the image. (a) of FIG. 14shows a schematic diagram serving to illustrate the intra framepredictive method used by H.264 and (b) of FIG. 14 shows the directionfor extending the pixel signal of the intra frame predictive method ofH. 264. In (a) of FIG. 14, block 901 is the target block and blocks 902to 904 are adjacent blocks, where these blocks contain pixel signalswhich have been regenerated in previous processing. Here, a regeneratedpixel group 905 which is adjacent to the target block boundary of block901 is used to generate a predictive signal in the nine directions whichare shown in (b) of FIG. 14. For example, in the case of direction “0”,a predictive signal is generated by extending the adjacent pixeldirectly above block 901 downward; in the case of direction “1”, apredictive signal is generated by extending the regenerated pixel to theleft of block 901 to the right and, in the case of direction “2”, theaverage value of all of the pixel values of the pixel group 905 isgenerated as a predictive signal. A more specific method when generatinga predictive signal appears in Non-Patent Document 1 hereinbelow, forexample. With H.264, the difference between each of nine predictivesignals generated in this manner and a pixel signal for the target blockis taken and the predictive signal generation method with the smallestdifference value is taken as the optimum predictive method (alsoreferred to as a ‘mode’).

When transmitting image data, it is necessary to transmit identificationinformation which indicates the optimum predictive method determined inthis manner for the recovery of image data to the transmission side.Here, the predictive method determined for the two blocks, namely block902 and block 903, is taken as the reference and information relating tothe optimum predictive method of block 901 is encoded. In other words,the identification information for the method of predicting block 902and the identification information for the method of predicting block903 are compared and the identification information with the smallestvalue is determined as the reference mode information. Further, theidentification information relating to the optimum method of predictingthe target block is encoded relatively from this reference modeinformation.

-   Patent Document 1: U.S. Patent Publication No. 6148109-   Non-Patent Document 1: Iain E. G. Richardson, “H.264 and MPEG4 video    compression”, Wiley 2003, pages pp. 177 to 183.

DISCLOSURE OF INVENTION Problem to be Solved by the Invention

However, in the case of a method of encoding using intra framepredictive signal generation in a pixel domain as per H.264, although itis possible to provide multiple predictive methods for improving theefficiency of encoding pixel signals, because it is necessary to uselong code length information when encoding the mode information foridentifying the predictive method in this case, there is an increase inthe overall bit amount. In order to solve such a problem, as mentionedearlier, relative encoding with respect to the identificationinformation related to the adjacent block predictive method is carriedout. However, as a result of using two adjacent blocks, there is atendency for the generation of reference mode information at highaccuracy with respect to the optimum predictive method (of the targetblock) to be impossible and it is not possible to adequately suppressthe bit amount of the mode information.

In addition, in cases where adjacent blocks are encoded by means ofinterframe predictive encoding, target block mode information isrelatively encoded by referencing to a fixed mode information becausethe adjacent blocks do not possess intra frame prediction-related modeinformation. Interframe predictive encoding is a predictive encodingmethod which uses a predictive signal of minimal error from thereference image to the target block by taking a regenerated image whichis restored after being previously encoded as the reference image. Incases where adjacent blocks adopt interframe predictive encoding in thismanner, the encoding efficiency of the predictive method-related modeinformation when subjecting the target block to intra frame predictiveencoding drops.

Therefore, the present invention was conceived in view of these problemsand an object of the present invention is to provide an image predictionencoding device, an image prediction decoding device, an imageprediction encoding method, an image prediction decoding method, animage prediction encoding program, and an image prediction decodingprogram which enable efficient encoding processing or decodingprocessing by reducing predictive method-related mode information forgenerating an intra frame predictive signal in a pixel domain.

Means for Solving the Problem

In order to solve the above problem, the image prediction encodingdevice of the present invention is an image prediction encoding devicewhich divides an image into a plurality of regions, generates an intraframe predictive signal with respect to a pixel signal contained in atarget area which is a processing target among the areas, and encodes aresidual signal between the pixel signal of the target area and theintra frame predictive signal, and the image prediction encoding devicecomprises first predictive method determination means which derives,based on processed data corresponding to adjacent areas comprisingregenerated pixel signals and adjacent to the target area, a predictivemethod which generates an intra frame predictive signal which has a highcorrelation to the pixel signals of the adjacent areas from among apredetermined plurality of predictive methods for generating the intraframe predictive signal, and determines the predictive method as a firstpredictive method; predictive signal generation means which generatesthe intra frame predictive signal on the basis of the first predictivemethod determined by the first predictive method determination means;and image encoding means which encodes a residual signal of the pixelsignal of the target area on the basis of the intra frame predictivesignal generated by the predictive signal generation means.

The image prediction encoding method of the present invention is animage prediction encoding method which divides an image into a pluralityof areas, generates an intra frame predictive signal with respect to apixel signal contained in a target area which is a processing targetamong the areas, and encodes a residual signal between the pixel signalof the target area and the intra frame predictive signal, and the imageprediction encoding method comprises a first predictive methoddetermination step in which first predictive method determination meansderives, based on processed data corresponding to adjacent areascomprising regenerated pixel signals and adjacent to the target area, apredictive method which generates an intra frame predictive signal whichhas a high correlation to the pixel signals of the adjacent areas fromamong a predetermined plurality of predictive methods for generating theintra frame predictive signal, and determines the predictive method as afirst predictive method; a predictive signal generation step in whichpredictive signal generation means generates the intra frame predictivesignal on the basis of the first predictive method determined in thefirst predictive method determination step; and an image encoding stepin which image encoding means encodes a residual signal of the pixelsignal of the target area on the basis of the intra frame predictivesignal generated in the predictive signal generation step.

The image prediction encoding program of the present invention is animage prediction encoding program which divides an image into aplurality of areas, generates an intra frame predictive signal withrespect to a pixel signal contained in a target area which is aprocessing target among the areas, and encodes a residual signal betweenthe pixel signal of the target area and the intra frame predictivesignal, and the image prediction encoding program causes a computer tofunction as first predictive method determination means which derives,based on processed data corresponding to adjacent areas comprisingregenerated pixel signals and adjacent to the target area, a predictivemethod which generates an intra frame predictive signal which has a highcorrelation to the pixel signals of the adjacent areas from among apredetermined plurality of predictive methods for generating the intraframe predictive signal, and determines the predictive method as a firstpredictive method; predictive signal generation means which generatesthe intra frame predictive signal on the basis of the first predictivemethod determined by the first predictive method determination means;and image encoding means which encodes a residual signal of the pixelsignal of the target area on the basis of the intra frame predictivesignal generated by the predictive signal generation means.

According to the image prediction encoding device, image predictionencoding method, and image prediction encoding program, a firstpredictive method for generating, for regenerated adjacent areas whichare adjacent to the target area which is the encoding target, apredictive signal which has a high correlation to the pixel signals ofthe adjacent areas by using data processed in accordance with theadjacent areas is derived, an intra frame predictive signal of thetarget area is generated on the basis of the predictive method, and aresidual signal for the target area is encoded by using the intra framepredictive signal. As a result, because the predictive method for theintra frame predictive signal is derived simply by using processed datacorresponding to regenerated adjacent areas, there is no need totransmit mode information identifying the predictive method and theoverall encoding efficiency improves.

Alternatively, the image prediction encoding device of the presentinvention is an image prediction encoding device which divides an imageinto a plurality of areas, generates an intra frame predictive signalwith respect to a pixel signal contained in a target area which is aprocessing target among the areas, and encodes a residual signal betweenthe pixel signal of the target area and the intra frame predictivesignal, and the image prediction encoding device comprises firstpredictive method determination means which derives, based on processeddata corresponding to adjacent areas comprising regenerated pixelsignals and adjacent to the target area, a predictive method whichgenerates an intra frame predictive signal which has a high correlationto the pixel signals of the adjacent areas from among a predeterminedplurality of predictive methods for generating the intra framepredictive signal, and determines the predictive method as a firstpredictive method; second predictive method determination means whichgenerates a plurality of predictive signals corresponding to apredetermined plurality of predictive methods for the target area anddetermines a second predictive method which is suitable for the targetarea from among the plurality of predictive methods in accordance with apredetermined evaluation standard; predictive signal generation meanswhich generates the intra frame predictive signal on the basis of thesecond predictive method determined by the second predictive methoddetermination means; mode information encoding means which relativelyencodes the second predictive method on the basis of the firstpredictive method; and image encoding means which encodes a residualsignal of the pixel signal of the target area on the basis of the intraframe predictive signal generated by the predictive signal generationmeans.

Alternatively, the image prediction encoding method of the presentinvention is an image prediction encoding method which divides an imageinto a plurality of areas, generates an intra frame predictive signalwith respect to a pixel signal contained in a target area which is aprocessing target among the areas, and encodes a residual signal betweenthe pixel signal of the target area and the intra frame predictivesignal, and the image prediction encoding method comprises a firstpredictive method determination step in which first predictive methoddetermination means derives, based on processed data corresponding toadjacent areas comprising regenerated pixel signals and adjacent to thetarget area, a predictive method which generates an intra framepredictive signal which has a high correlation to the pixel signals ofthe adjacent areas from among a predetermined plurality of predictivemethods for generating the intra frame predictive signal, and determinesthe predictive method as a first predictive method; a second predictivemethod determination step in which second predictive methoddetermination means generates a plurality of predictive signalscorresponding to a predetermined plurality of predictive methods for thetarget area and determines a second predictive method which is suitablefor the target area from among the plurality of predictive methods inaccordance with a predetermined evaluation standard; a predictive signalgeneration step in which predictive signal generation means generatesthe intra frame predictive signal on the basis of the second predictivemethod determined in the second predictive method determination step; amode information encoding step in which mode information encoding meansrelatively encodes the second predictive method on the basis of thefirst predictive method; and an image encoding step in which imageencoding means encodes a residual signal of the pixel signal of thetarget area on the basis of the intra frame predictive signal generatedby the predictive signal generation means.

Alternatively, the image prediction encoding program of the presentinvention is an image prediction encoding program which divides an imageinto a plurality of areas, generates an intra frame predictive signalwith respect to a pixel signal contained in a target area which is aprocessing target among the areas, and encodes a residual signal betweenthe pixel signal of the target area and the intra frame predictivesignal, and the image prediction encoding program causes a computer tofunction as first predictive method determination means which derives,based on processed data corresponding to adjacent areas comprisingregenerated pixel signals and adjacent to the target area, a predictivemethod which generates an intra frame predictive signal which has a highcorrelation to the pixel signals of the adjacent areas from among apredetermined plurality of predictive methods for generating the intraframe predictive signal, and determines the predictive method as a firstpredictive method; second predictive method determination means whichgenerates a plurality of predictive signals corresponding to apredetermined plurality of predictive methods for the target area anddetermines a second predictive method which is suitable for the targetarea from among the plurality of predictive methods in accordance with apredetermined evaluation standard; predictive signal generation meanswhich generates the intra frame predictive signal on the basis of thesecond predictive method determined by the second predictive methoddetermination means; mode information encoding means which relativelyencodes the second predictive method on the basis of the firstpredictive method; and image encoding means which encodes a residualsignal of the pixel signal of the target area on the basis of the intraframe predictive signal generated by the predictive signal generationmeans.

According to the image prediction encoding device, image predictionencoding method, and image prediction encoding program, a firstpredictive method for generating, for regenerated adjacent areas whichare adjacent to the target area which is the encoding target, apredictive signal which has a high correlation to the pixel signals ofthe adjacent areas by using data processed in accordance with theadjacent areas is derived, a second predictive method for generating anintra frame predictive signal of the target area is relatively encodedon the basis of the first predictive method, and a residual signal forthe target area is encoded by using the intra frame predictive signal.The predictive method which is derived for the adjacent areas by usingprocessed data corresponding to the regenerated adjacent areas have ahigh probability of being close to the optimum predictive method for thetarget area. Hence, by encoding the predictive method-related modeinformation of the target area relatively by using this predictivemethod, the bit amount for encoding of the mode information identifyingthe predictive method is reduced and the overall encoding efficiencyimproves.

Furthermore, the first predictive method determination means preferablygenerates a plurality of predictive signals for the adjacent areascorresponding to a predetermined plurality of predictive methods anddetermines the first predictive method from among the plurality ofpredictive methods in accordance with a predetermined evaluationstandard. In this case, a predictive method which is close to theoptimum predictive method for the target area can be easily specified onthe basis of a regenerated pixel signal by determining the firstpredictive method for the adjacent areas from among the plurality ofpredictive methods in accordance with a predetermined evaluationstandard.

In addition, the first predictive method determination means preferablyuses three or more predictive methods which are previously determinedaccording to the adjacent areas to determine the first predictive methodfor the adjacent areas in accordance with a predetermined evaluationstandard. If such a constitution is adopted, a predictive method whichis close to the optimum predictive method for the target area can beeasily specified by using the three or more predictive methodsdetermined for the adjacent areas to determine the first predictivemethod in accordance with a predetermined evaluation standard.

The image prediction decoding device of the present invention is animage prediction decoding device which divides an image into a pluralityof areas, generates an intra frame predictive signal with respect to apixel signal contained in a target area which is a processing targetamong the areas, and restores the pixel signal of the target area bycombining a residual signal relating to the target area contained incompressed image data and the intra frame predictive signal, and theimage prediction decoding device comprises first predictive methoddetermination means which derives, based on processed data correspondingto adjacent areas comprising regenerated pixel signals and adjacent tothe target area, a predictive method which generates an intra framepredictive signal which has a high correlation to the pixel signals ofthe adjacent areas from among a predetermined plurality of predictivemethods for generating the intra frame predictive signal, and determinesthe predictive method as a first predictive method; predictive signalgeneration means which generates the intra frame predictive signal onthe basis of the first predictive method determined by the firstpredictive method determination means; restoration means which extractsa residual signal relating to the target area from the compressed imagedata to restore a regenerated residual signal; and image restorationmeans which restores the pixel signal of the target area by combiningthe intra frame predictive signal and the regenerated residual signalrestored by the restoration means.

The image prediction decoding method of the present invention is animage prediction decoding method which divides an image into a pluralityof areas, generates an intra frame predictive signal with respect to apixel signal contained in a target area which is a processing targetamong the areas, and restores the pixel signal of the target area bycombining a residual signal relating to the target area contained incompressed image data and the intra frame predictive signal, and theimage prediction decoding method comprises a first predictive methoddetermination step in which first predictive method determination meansderives, based on processed data corresponding to adjacent areascomprising regenerated pixel signals and adjacent to the target area, apredictive method which generates an intra frame predictive signal whichhas a high correlation to the pixel signals of the adjacent areas fromamong a predetermined plurality of predictive methods for generating theintra frame predictive signal, and determines the predictive method as afirst predictive method; a predictive signal generation step in whichpredictive signal generation means generates the intra frame predictivesignal on the basis of the first predictive method determined in thefirst predictive method determination step; a restoration step in whichrestoration means extracts a residual signal relating to the target areafrom the compressed image data to restore a regenerated residual signal;and an image restoration step in which image restoration means restoresthe pixel signal of the target area by combining the intra framepredictive signal and the regenerated residual signal restored in therestoration step.

The image prediction decoding program of the present invention is animage prediction decoding program which divides an image into aplurality of areas, generates an intra frame predictive signal withrespect to a pixel signal contained in a target area which is aprocessing target among the areas, and restores the pixel signal of thetarget area by combining a residual signal relating to the target areacontained in compressed image data and the intra frame predictivesignal, and the image prediction decoding program causes a computer tofunction as first predictive method determination means which derives,based on processed data corresponding to adjacent areas comprisingregenerated pixel signals and adjacent to the target area, a predictivemethod which generates an intra frame predictive signal which has a highcorrelation to the pixel signals of the adjacent areas from among apredetermined plurality of predictive methods for generating the intraframe predictive signal, and determines the predictive method as a firstpredictive method; predictive signal generation means which generatesthe intra frame predictive signal on the basis of the first predictivemethod determined by the first predictive method determination means;restoration means which extracts a residual signal relating to thetarget area from the compressed image data to restore a regeneratedresidual signal; and image restoration means which restores the pixelsignal of the target area by combining the intra frame predictive signaland the regenerated residual signal restored by the restoration means.

According to the image prediction decoding device, image predictiondecoding method, and image prediction decoding program, a firstpredictive method for generating, for regenerated adjacent areas whichare adjacent to the target area which is the decoding target, apredictive signal which has a high correlation to the pixel signals ofthe adjacent areas by using data processed in accordance with theadjacent areas is derived, an intra frame predictive signal of thetarget area is generated on the basis of the predictive method, and apixel signal for the target area is restored from a regenerated residualsignal obtained by restoring the residual signal of the target area byusing the intra frame predictive signal. As a result, because thepredictive method for the intra frame predictive signal is derivedsimply by using processed data corresponding to regenerated adjacentareas, there is no need to transmit mode information identifying thepredictive method and the overall encoding efficiency improves.

Alternatively, the image prediction decoding device of the presentinvention is an image prediction decoding device which divides an imageinto a plurality of areas, generates an intra frame predictive signalwith respect to a pixel signal contained in a target area which is aprocessing target among the areas, and restores the pixel signal of thetarget area by combining a residual signal relating to the target areacontained in compressed image data and the intra frame predictivesignal, and the image prediction decoding device comprises firstpredictive method determination means which derives, based on processeddata corresponding to adjacent areas comprising regenerated pixelsignals and adjacent to the target area, a predictive method whichgenerates an intra frame predictive signal which has a high correlationto the pixel signals of the adjacent areas from among a predeterminedplurality of predictive methods for generating the intra framepredictive signal, and determines the predictive method as a firstpredictive method; predictive method deriving means which extracts arelative predictive method which is relative information identifying thepredictive method relating to the target area from the compressed imagedata and derives a second predictive method for the target area on thebasis of the first predictive method and the relative predictive method;predictive signal generation means which generates the intra framepredictive signal on the basis of the second predictive method derivedby the predictive method deriving means; restoration means whichextracts a residual signal relating to the target area from thecompressed image data to restore a regenerated residual signal; andimage restoration means which restores the pixel signal of the targetarea by combining the intra frame predictive signal and the regeneratedresidual signal restored by the restoration means.

Alternatively, the image prediction decoding method of the presentinvention is an image prediction decoding method which divides an imageinto a plurality of areas, generates an intra frame predictive signalwith respect to a pixel signal contained in a target area which is aprocessing target among the areas, and restores the pixel signal of thetarget area by combining a residual signal relating to the target areacontained in compressed image data and the intra frame predictivesignal, and the image prediction decoding method comprises a firstpredictive method determination step in which first predictive methoddetermination means derives, based on processed data corresponding toadjacent areas comprising regenerated pixel signals and adjacent to thetarget area, a predictive method which generates an intra framepredictive signal which has a high correlation to the pixel signals ofthe adjacent areas from among a predetermined plurality of predictivemethods for generating the intra frame predictive signal, and determinesthe predictive method as a first predictive method; a predictive methodderiving step in which predictive method deriving means extracts arelative predictive method which is relative information identifying thepredictive method relating to the target area from the compressed imagedata and derives a second predictive method for the target area on thebasis of the first predictive method and the relative predictive method;a predictive signal generation step in which predictive signalgeneration means generates the intra frame predictive signal on thebasis of the second predictive method derived in the predictive methodderiving step; a restoration step in which restoration means extracts aresidual signal relating to the target area from the compressed imagedata to restore a regenerated residual signal; and an image restorationstep in which image restoration means restores the pixel signal of thetarget area by combining the intra frame predictive signal and theregenerated residual signal restored by the restoration means.

Alternatively, the image prediction decoding program of the presentinvention is an image prediction decoding program which divides an imageinto a plurality of areas, generates an intra frame predictive signalwith respect to a pixel signal contained in a target area which is aprocessing target among the areas, and restores the pixel signal of thetarget area by combining a residual signal relating to the target areacontained in compressed image data and the intra frame predictivesignal, and the image prediction decoding program causes a computer tofunction as first predictive method determination means which derives,based on processed data corresponding to adjacent areas comprisingregenerated pixel signals and adjacent to the target area, a predictivemethod which generates an intra frame predictive signal which has a highcorrelation to the pixel signals of the adjacent areas from among apredetermined plurality of predictive methods for generating the intraframe predictive signal, and determines the predictive method as a firstpredictive method; predictive method deriving means which extracts arelative predictive method which is relative information identifying thepredictive method relating to the target area from the compressed imagedata and derives a second predictive method for the target area on thebasis of the first predictive method and the relative predictive method;predictive signal generation means which generates the intra framepredictive signal on the basis of the second predictive method derivedby the predictive method deriving means; restoration means whichextracts a residual signal relating to the target area from thecompressed image data to restore a regenerated residual signal; andimage restoration means which restores the pixel signal of the targetarea by combining the intra frame predictive signal and the regeneratedresidual signal restored by the restoration means.

According to the image prediction decoding device, image predictiondecoding method, and image prediction decoding program, a firstpredictive method for generating, for regenerated adjacent areas whichare adjacent to the target area which is the decoding target, apredictive signal which has a high correlation to the pixel signals ofthe adjacent areas by using data processed in accordance with theadjacent areas is derived, a second predictive method for the targetarea is derived on the basis of the first predictive method and therelative predictive method and an intra frame predictive signal isgenerated, and the intra frame predictive signal is used to restore thepixel signal of the target area from the regenerated residual signalobtained by restoring the residual signal of the target area. Thepredictive method which is derived for the adjacent areas by usingprocessed data corresponding to the regenerated adjacent areas have ahigh probability of being close to the optimum predictive method for thetarget area. Hence, by restoring the predictive method-related modeinformation of the target area relatively by using this predictivemethod, the bit amount for encoding of the mode information (relativepredictive method) identifying the predictive method is reduced and theoverall decoding efficiency improves.

Furthermore, the first predictive method determination means preferablygenerates a plurality of predictive signals for the adjacent areascorresponding to a predetermined plurality of predictive methods anddetermines the first predictive method from among the plurality ofpredictive methods in accordance with a predetermined evaluationstandard. In this case, a predictive method which is close to theoptimum predictive method for the target area can be easily specified onthe basis of a regenerated pixel signal by determining the firstpredictive method for the adjacent areas from among the plurality ofpredictive methods in accordance with a predetermined evaluationstandard.

In addition, the first predictive method determination means preferablyuses three or more predictive methods which are previously determinedaccording to the adjacent areas to determine the first predictive methodfor the adjacent areas in accordance with a predetermined evaluationstandard. If such a constitution is adopted, a predictive method whichis close to the optimum predictive method for the target area can beeasily specified by using the three or more predictive methodsdetermined for the adjacent areas to determine the first predictivemethod in accordance with a predetermined evaluation standard.

Effect of the Invention

The present invention permits efficient encoding processing or decodingprocessing by reducing predictive method-related mode information forgenerating an intra frame predictive signal in a pixel domain.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A block diagram which shows the constitution of an imagepredictive encoding device according to a preferred embodiment of thepresent invention.

FIG. 2 A block diagram which shows the constitution of the intra framepredictive signal generation method determination section in FIG. 1.

FIG. 3 A schematic diagram serving to illustrate processing to determinean R mode predictive method of an R mode determination section in FIG.2.

FIG. 4 A schematic diagram serving to illustrate processing to determinean L mode predictive method of an L mode determination section in FIG.2.

FIG. 5 A flowchart which shows processing to determine an L modepredictive method using the L mode determination section in FIG. 2.

FIG. 6 A flowchart which shows processing to determine the predictivesignal generation method of the intra frame predictive signal generationmethod determination section in FIG. 1.

FIG. 7 A block diagram which shows the constitution of an imagepredictive decoding device according to a preferred embodiment of thepresent invention.

FIG. 8 A block diagram which shows the constitution of a predictivemethod acquisition section in FIG. 7.

FIG. 9 A flowchart which shows acquisition processing to acquire apredictive signal generation method of the predictive method acquisitionsection in FIG. 7.

FIG. 10 A block diagram which shows a modified example of an intra framepredictive signal generation method determination section in FIG. 2.

FIG. 11 A block diagram which shows a modified example of the predictivemethod acquisition section in FIG. 8.

FIG. 12 A diagram which shows the hardware constitution of a computerfor executing the image predictive encoding program and the imagepredictive decoding program according to the embodiment of the presentinvention.

FIG. 13 A perspective view of the computer in FIG. 12.

FIG. 14 (a) is a schematic diagram serving to illustrate the intra framepredictive method used in H. 264 and (b) shows the direction forextending the pixel signal of the H. 264 intra frame predictive method.

LIST OF SYMBOLS

10 . . . IMAGE PREDICTIVE ENCODING DEVICE, 11 . . . INPUT TERMINAL, 12 .. . BLOCK DIVISION SECTION, 13 . . . INTER FRAME PREDICTIVE SIGNALGENERATION METHOD DETERMINATION SECTION, 14 . . . INTER FRAME PREDICTIVESIGNAL GENERATION SECTION, 15 . . . INTRA FRAME PREDICTIVE SIGNALGENERATION METHOD DETERMINATION SECTION, 16 . . . INTRA FRAME PREDICTIVESIGNAL GENERATION SECTION, 17 . . . SWITCHING SWITCH, 18 . . .SUBTRACTOR, 19 . . . TRANSFORM SECTION, 20 . . . QUANTIZATION SECTION,21 . . . REVERSE QUANTIZATION SECTION, 22 . . . INVERSE TRANSFORMSECTION, 23 . . . ADDER, 24 FRAME MEMORY, 25 . . . ENTROPY ENCODINGSECTION, 26 . . . OUTPUT TERMINAL, 41 . . . PREDICTIVE METHODDETERMINATION SECTION, 42 . . . PREDICTIVE SIGNAL GENERATION SECTION, 43. . . R MODE DETERMINATION SECTION, 44 . . . STORAGE SECTION, 45 . . .MODE INFORMATION PREDICTION SECTION, 46 . . . L MODE DETERMINATIONSECTION, 50 . . . IMAGE PREDICTIVE DECODING DEVICE, 51 . . . DATAANALYSIS SECTION, 52 . . . REVERSE QUANTIZATION SECTION, 53 . . .INVERSE TRANSFORM SECTION, 54 . . . ADDER, 55 . . . PREDICTIVE SIGNALGENERATION SECTION, 56 . . . FRAME MEMORY, 57 . . . PREDICTIVE METHODACQUISITION SECTION, 58 . . . INPUT TERMINAL, 59 . . . OUTPUT TERMINAL,61 . . . SWITCHING SWITCH, 64 . . . R MODE DETERMINATION SECTION, 65 . .. STORAGE SECTION, 66 . . . L MODE DETERMINATION SECTION, 67 . . . MODEINFORMATION GENERATION SECTION, 115 . . . INTRA FRAME PREDICTIVE SIGNALGENERATION METHOD DETERMINATION SECTION, 143 . . . F MODE DETERMINATIONSECTION, 157 . . . PREDICTIVE METHOD ACQUISITION SECTION, 164 . . . FMODE INFORMATION STORAGE SECTION, 301, 401, 901, . . . TARGET AREA, 302a to 302 f, 303 a to 303 c, 402 to 406, and 902 to 904 . . . ADJACENTAREA.

BEST MODE FOR CARRYING OUT THE INVENTION

Preferred embodiments of the image prediction encoding device and imageprediction decoding device according to the present invention will bedescribed in detail hereinbelow with reference to the drawings.

(Image Prediction Encoding Device)

FIG. 1 is a block diagram which shows the constitution of the imagepredictive encoding device according to a preferred embodiment of thepresent invention. The image predictive encoding device 10 shown in FIG.1 is constituted comprising an input terminal 11, a block divisionsection 12, an inter frame predictive signal generation methoddetermination section 13, an inter frame predictive signal generationsection 14, an intra frame predictive signal generation methoddetermination section 15, an intra frame predictive signal generationsection (predictive signal generation means) 16, a switching switch 17,a subtractor (image encoding means) 18, a transform section (imageencoding means) 19, a quantization section (image encoding means) 20, areverse quantization section 21, a inverse transform section 22, anadder 23, a frame memory 24, an entropy encoding section (image encodingmeans) 25, and an output terminal 26. The respective constituentelements of the image predictive encoding device 10 will be describedhereinbelow.

The block division section 12 receives an input of moving image datacomprising a plurality of frames' worth of image data from the inputterminal 11 and divides the image data into a plurality of areas. Morespecifically, the block division section 12 may divide the image datainto blocks consisting of 8×8 pixels but may also divide the image datainto blocks of another optional size and shape. The block divisionsection 12 outputs the divided block pixel signals via a line L2 to asubtractor 18 and via a line L3 to the inter frame predictive signalgeneration method determination section 13 and the intra framepredictive signal generation method determination section 15.

The inter frame predictive signal generation section 14 and intra framepredictive signal generation section 16 generates a predictive signalwhich predicts a target block image with respect to the areaconstituting the target for the encoding processing (called the ‘targetblock’ hereinbelow). Here, the inter frame predictive signal generationsection 14 uses a predictive method known as ‘inter frame prediction’ inthe generation of the predictive signal and the intra frame predictivesignal generation section 16 employs a predictive method known as ‘intraframe prediction’. In the case of ‘inter frame prediction’, a predictivemethod is determined by taking a regenerated image that has beenrestored after being previously encoded as the reference image andfinding motion information which supplies the predictive signal with thesmallest error with respect to the target block from the reference image(called ‘motion detection’ processing). In contrast, in ‘intra frameprediction’, an intra frame predictive signal is generated by means of apredetermined method by using regenerated pixel values which arespatially adjacent to the target block. This predictive method can alsobe applied to the encoding and decoding of still images.

The inter frame predictive signal generation method determinationsection 13 determines an inter frame predictive method by performing theaforementioned motion detection on the basis of a reference image whichis input from the frame memory 24 via a line L11 and a target blockpixel signal which is input via line L3. Here, the inter framepredictive signal generation method determination section 13 mayredivide the target block to determine the inter frame predictive methodfor the redivided small areas and is able to select the division methodwith the greatest efficiency for the whole of the target block fromvarious area division methods. In addition, a plurality of images whichare restored after being previously encoded may also be used asreference images. This motion detection method is similar to either ofthe conventional MPEG2, MPEG4 and H.264 methods and a detaileddescription thereof is therefore omitted. The inter frame predictivesignal generation method determination section 13 sends the determinedmotion information and small area division method to the inter framepredictive signal generation section 14 via a line L12 and sends thedetermined motion information and small area division method to theentropy encoding section 25 via a line L14. In contrast, the inter framepredictive signal generation section 14 generates a predictive signal onthe basis of the small-area division method, the motion informationcorresponding to each of the small areas, and a reference image which isacquired from the frame memory 24 and sends the predictive signal to thesubtractor 18 and adder 23 via a terminal 17 a and the switching switch17.

The intra frame predictive signal generation method determinationsection 15 determines the intra frame prediction predictive method(subsequently described in detail) on the basis of the target blockpixel signal input via line L3 and the reference image input from theframe memory 24 via a line L10. The intra frame predictive signalgeneration method determination section 15 sends information relating tothe determined predictive method to the intra frame predictive signalgeneration section 16 via line L13 and to the entropy encoding section25 via line L14 or L15. In response, the intra frame predictive signalgeneration section 16 generates a predictive signal by means of apredetermined method on the basis of the predictive method-relatedinformation and the regenerated pixel signals in the same frame acquiredfrom the frame memory 24 and sends the predictive signal to thesubtractor 18 and adder 23 via a terminal 17 b and the switching switch17.

Given the predictive signals sent from the inter frame predictive signalgeneration section 14 and from intra frame predictive signal generationsection 16, the switching switch 17 judges which of the predictivesignals has a smaller error with respect to the target area pixelsignal, and selects the predictive signal with the smaller measurementerror in accordance with the judgment result before outputting same tothe subtractor 18 and adder 23. However, in cases where all of theblocks are processed by means of intra frame prediction because aprevious image does not exist for the first frame, the switching switch17 is always connected to terminal 17 b of the intra frame predictivesignal generation section 16 when processing the first image. Similarly,in cases where a frame directly following a scene change is processedand in cases where there is a need to introduce the intra frameprediction image periodically, the switching switch 17 also selects thepredictive signal generated by the intra frame prediction for the wholeframe.

The subtractor 18 generates a residual signal by subtracting thepredictive signal which is input via the switching switch 17 from thetarget block pixel signal input from the block division section 12. Thisresidual signal is output to the transform section 19 via line L4 andthe transform section 19 generates a transform coefficient by performingdiscrete cosine transform on the residual signal. The transformcoefficient is output to the quantization section 20 via line L5 and,after quantizing the transform coefficient, the quantization section 20outputs the quantized transform coefficient to the entropy encodingsection 25 and the reverse quantization section 21 via line L6. Theentropy encoding section 25 encodes the quantized transform coefficient,combines it with the motion information output by the inter framepredictive signal generation method determination section 13 andinformation relating to the small-area division method or relating tothe predictive method which is output by the intra frame predictivesignal generation method determination section 15 and outputs same tothe output terminal 26.

The reverse quantization section 21 performs reverse quantization on thequantized transform coefficient to restore same to the transformcoefficient and outputs the transform coefficient to the inversetransform section 22 via a line L7. The inverse transform section 22restores the residual signal by subjecting the transform coefficient toreverse discrete cosine transform. The adder 23 regenerates a targetblock pixel signal by combining this residual signal with the predictivesignal input via line L17 and stores the pixel signal in the framememory 24 via a line L9. The target block pixel signal stored in theframe memory 24 is utilized to generate the target block predictivesignal which is processed next.

The constitution of the intra frame predictive signal generation methoddetermination section 15 will be described next in detail. FIG. 2 is ablock diagram which shows the constitution of the intra frame predictivesignal generation method determination section 15. As shown in FIG. 2,the intra frame predictive signal generation method determinationsection 15 comprises a predictive method determination section (secondpredictive method determination means, mode information encoding means)41, a predictive signal generation section (second predictive methoddetermination means) 42, an R mode determination section (firstpredictive method determination means) 43, a storage section 44, a modeinformation prediction section (mode information encoding means) 45, andan L mode determination section (first predictive method determinationmeans) 46.

The predictive signal generation section 42 uses regenerated pixelsadjacent to the target block which are read from the frame memory 24 vialine L10 to generate a predictive signal by means of nine methods. Morespecifically, as shown in (a) of FIG. 14, the predictive signalgeneration section 42 uses the regenerated pixel group 905 adjacent tothe boundary of block 901 which is the target block to generate apredictive signal for the block 901 in the nine directions shown in (b)of FIG. 14. For example, in the case of direction θ, a predictive signalis generated by extending the adjacent pixel directly above block 901downward and, in the case of direction 1, a predictive signal isgenerated by extending the regenerated pixel to the left of block 901 tothe right. The details of the method for generating the predictivesignal appear in U.S. Pat. No. 6,148,109, for example. The predictivesignal generation section 42 sends the nine predictive signals thusgenerated to a predictive method determination section 41 via a lineL32. In addition to generating the nine predictive signals, thepredictive signal generation section 42 may also generate a greaternumber or a smaller number of predictive signals. The predictive signalsmay also be generated by means of a different method from that mentionedabove, such as spline extrapolation, for example.

An R mode determination section 43 uses a predetermined evaluationstandard to derive one predictive method for generating an intra framepredictive signal which is highly correlated to the adjacent area pixelsignals from among the nine predictive methods (see (b) of FIG. 14) onthe basis of the predictive method-related mode information determinedin accordance with a regenerated adjacent area. In other words, the Rmode determination section 43 acquires a plurality of predictivemethod-related mode information for the previously processed blocksstored in the storage section 44 and determines the predictive method bymeans of a predetermined method (R mode prediction). Here, the storagesection 44 stores predictive method-related mode information which wasdetermined in accordance with previously processed blocks via a lineL34.

FIG. 3 is a schematic diagram serving to illustrate processing todetermine the R mode predictive method. In FIG. 3, the target block is301. 302 and 303 represent areas of adjacent pixels which have beenpreviously encoded and restored. Area 302 comprises blocks 302 a to 302f and area 303 comprises blocks 303 a to 303 c, and these blocks possesspredictive method-related mode information which is used when encodingeach of these blocks. Area 302 is an area comprising blocks of 12(horizontal)×4 (vertical) pixels and area 303 is an area which comprisesblocks of 4×4 pixels. However, these areas may also be areas of anothersize and shape. The adjacent blocks of the prior art are only block 302d which is above the target block 301 and the block to the left oftarget block 301 (not shown) and the description will focus on thedifferences from this embodiment.

Therefore, the R mode determination section 43 determines the predictivemethod which corresponds with mode information of the highest incidenceamong the intra frame prediction-related mode information items owned bythe blocks 302 a to 302 f and 303 a to 303 c stored in the storagesection 44 as the R mode predictive method which is the predictivemethod with the highest correlation to all the pixels adjacent to thetarget block. The R mode determination section 43 may also determine theR mode predictive method on the basis of the mode information determinedin accordance with three or more blocks by using another method and mayuse an area of a different size and shape as the area obtained byjoining areas 302 and 303. The R mode determination section 43 sends theR mode predictive method-related information to the predictive methoddetermination section 41 via a line L31. The R mode determinationsection 43 may use a predetermined function to process the R modepredictive method-related identification information as the target andsend the identification information obtained as a result of theprocessing to the predictive method determination section 41. A functionthat may be cited as such a function is a function to add ±n (where n isan optional integer) to the identification information in cases wherethe identification information comprises numerical value information.

When a target block pixel signal is input via line L3, the predictivemethod determination section 41 finds the difference between the ninepredictive signals sent via a line L32 and the target block signal anddetermines the predictive signal which supplies the smallestdifferential value as the optimum predictive signal. The predictivemethod determination section 41 sends predictive method-related modeinformation according to the optimum predictive signal to the intraframe predictive signal generation section 16 (see FIG. 1) via line L13and sends the predictive method-related mode information to a modeinformation prediction section 45 via a line L35.

In addition, the predictive method determination section 41 encodes thepredictive method-related mode information pertaining to the optimumpredictive signal on the basis of the R mode predictive method-relatedinformation. More specifically, the predictive method determinationsection 41 performs encoding to produce identification information ‘ 0’in cases where the optimum predictive method coincides with the R modepredictive method and performs encoding to produce identificationinformation ‘1’ in other cases, and sends the identification informationto the entropy encoding section 25 (see FIG. 1) via line L15. In otherwords, the predictive method determination section 41 need not sendinformation other than the identification information to a downstreamprocessing section in cases where the identification information is ‘0’. This is because the intra frame predictive signal generation section16 generates an intra frame predictive signal by means of the samepredictive method as the predictive method determined by means of the Rmode predictive method and it is therefore possible to determine thepredictive method by means of the same R mode determination method onthe regeneration side. In contrast, in cases where the identificationinformation is ‘1’, it is necessary to also send predictivemethod-related mode information (the details will be providedsubsequently). The predictive method determination section 41 may alsooperate to determine the R mode predictive method as the optimumpredictive method without further processing and send the R modepredictive method to the intra frame predictive signal generationsection 16.

The L mode determination section 46 uses a predetermined evaluationstandard to derive one predictive method for generating an intra framepredictive signal which is highly correlated to the adjacent area pixelsignals from among the nine predictive methods (see (b) of FIG. 14) onthe basis of the regenerated pixel signals in accordance with an areacomprising adjacent areas. In other words, the L mode determinationsection 46 determines once again the predictive method for adjacentareas which are adjacent to the target block while referencing the datastored in the frame memory 24 (L mode prediction). FIG. 4 is a schematicdiagram which serves to illustrate processing to determine the L modepredictive method by means of the L mode determination section 46. Block401 is the target area. Blocks 402 to 404 are regenerated adjacentblocks. The area 405 which is filled with oblique lines is an adjacentarea of the target block 401. Area 405 is a reverse L-shaped area whichencloses four pixels above the boundary of the target block and fourpixels to the left of the boundary of the target block but an adjacentarea 405 of a different size and shape may also be employed. The L modedetermination section 46 uses a pixel group of an area 406 which isadjacent to the reverse L-shaped area to generate nine predictivesignals for the reverse L-shaped area 405 by means of the samepredictive method as the method illustrated in FIG. 14. In addition, theL mode determination section 46 calculates the difference between thesignal of the reverse L-shaped area 405 and nine predictive signals anddetermines the predictive mode information which corresponds with thepredictive method which supplies the predictive signal with the smallestdifferential (prediction information relating to the first predictivemethod) as the predictive method which is highly correlated to thepixels of the reverse L-shaped area 405 of the target block.

The flow of the processing of the L mode predictive method by the L modedetermination section 46 will be described hereinbelow with reference toFIG. 5. First, the L mode determination section 46 generates ninepredictive signals by using a pixel group in area 406 for adjacent area405 which is adjacent to target area 401 (step S11). Thereafter, the Lmode determination section 46 finds each of the differential valuesbetween the signal of adjacent area 405 of the reverse L-shaped area andthe nine predictive signals (step S12). Thereafter, the L modedetermination section 46 takes the predictive method which correspondswith the predictive signal which supplies the smallest differentialvalue as the optimum L mode (first predictive method) (step S13).Finally, the L mode determination section 46 outputs informationrelating to the optimum L mode to the mode information predictionsection 45 and storage section 44 (step S14). The L mode determinationsection 46 may use a predetermined function to process L mode predictivemethod-related identification information as the target and send theidentification information obtained as a result of the processing to themode information prediction section 45 and the storage section 44. Afunction that may be cited as such a function is a function to add ±n(where n is an optional integer) to the identification information incases where the identification information comprises numerical valueinformation.

Returning now to FIG. 2, the mode information prediction section 45encodes predictive method-related mode information pertaining to theoptimum predictive signal on the basis of the optimum L mode-relatedinformation input from the L mode determination section 46. Here, themode information prediction section 45 receives an input of firstpredictive method-related information which is sent from the L modedetermination section 46 and target block optimum predictivemethod-related information which is sent from the predictive methoddetermination section 41. The mode information prediction section 45relatively encodes the target block optimum predictive method-relatedmode information with respect to the optimum L mode-related information.A method of performing relative encoding that may be cited is a methodthat performs encoding by finding the differential value between modeinformation representing the optimum predictive method for the targetblock and mode information representing the optimum L mode. However,other methods may also be applied. The mode information predictionsection 45 sends the relative prediction information obtained in thismanner to the entropy encoding section 25 via a line L14.

The method of determining the predictive signal generation method of theintra frame predictive signal generation method determination section 15will be described next with reference to FIG. 6. First, the predictivesignal generation section 42 generates nine intra frame predictivesignals by means of the above method for the target block (step S01).Thereafter, the predictive method determination section 41 finds thedifference between the target block image and the nine predictivesignals (step S02). The predictive method determination section 41 thendetermines the predictive method which supplies the smallestdifferential value as the optimum predictive mode (step S03). However,the R mode determination section 43 determines the optimum R modepredictive method by means of the above method (step S04). Here, becausethe R mode predictive method thus determined is determined based on thepreviously determined mode, this mode corresponds to any of nine modes.Thereafter, the predictive method determination section 41 compares theR mode predictive method with the optimum predictive mode determined instep S03 and judges whether the two coincide (step S05). In cases wherethe R mode predictive method and the optimum predictive method are thesame (step S05; YES), the predictive method determination section 41outputs identification information ‘ 0’ which indicates that the R modepredictive method is the predictive method used in the generation of theintra frame predictive signal (step S06). However, in cases where theoptimum predictive mode does not coincide with the R mode predictivemethod (step S05; NO), the L mode determination section 46 determinesthe L mode predictive method by means of the above method (step S07). Inaddition, the mode information prediction section 45 encodes therelative predictive method which is relative information for the optimumpredictive mode with respect to the L mode predictive method-relatedinformation (step S08). Finally, the mode information prediction section45 outputs the relative prediction information (step S09).

With the image predictive encoding device 10 described earlier, the Rmode and L mode predictive methods are derived by using data processedin accordance with the adjacent area with respect to regeneratedadjacent areas which are adjacent to the target area which is theencoding target, the optimum predictive method for generating an intraframe predictive signal for the target area is encoded on the basis ofthe predictive method, and the residual signal of the target area isencoded by using an intra frame predictive signal. The R mode and L modepredictive methods which are derived for the adjacent areas by using thedata corresponding to regenerated adjacent areas have a high probabilityof being close to the optimum predictive method for the target area.Hence, by encoding the predictive method-related mode information of thetarget area relatively by using the R mode and L mode predictivemethods, the bit amount for encoding of the mode information identifyingthe predictive method is reduced and the overall encoding efficiencyimproves.

In particular, in cases where the predictive method is determined on apredetermined evaluation standard by using three or more predictivemethod-related information items which a plurality of adjacent blocksadjacent to the target block each possess as per R mode, there is a highprobability that the predictive method will be close to the originalpredictive method of the target area. Therefore, because this predictivemethod can be taken as the target area predictive method, there is noneed to transmit mode information for identifying the predictive method(information identifying nine modes shown in (b) of FIG. 14, forexample). As a result, the bit amount according to the mode informationcan be reduced by means of simple processing.

Furthermore, in cases where the predictive method which was determinedfrom the nine predictive methods for the areas adjacent to the targetblock is used as per L mode, there is a high correlation to the targetblock predictive method and the target block mode information can bemore efficiently encoded on the basis of the predictive method. As aresult, the effect of reducing the bit amount pertaining to the modeinformation increases. Furthermore, in cases where the areas adjacent tothe target block are subjected to inter frame predictive encoding, evenwhen the adjacent blocks do not have intra frame prediction information,information relating to a predictive method determined from a pluralityof predictive methods for the areas adjacent to the target block or apredictive method which three or more of the adjacent blocks eachpossess is used to determine a predictive method on a predeterminedevaluation standard. Then, the target area prediction information isencoded based on the determined predictive method. As a result, thepredictive method-related information of the target block can be moreefficiently encoded.

(Image Prediction Decoding Device)

FIG. 7 is a block diagram which shows the constitution of the imagepredictive decoding device according to a preferred embodiment of thepresent invention. The image predictive decoding device 50 shown in FIG.7 is constituted comprising an input terminal 58, a data analysissection (restoration means) 51, a reverse quantization section(restoration means) 52, a inverse transform section (restoration means)53, an adder (image decoding means) 54, a predictive signal generationsection (predictive signal generation means) 55, a frame memory 56, apredictive method acquisition section 57, and an output terminal 59. Therespective constituent elements of the image predictive decoding device50 will be described hereinbelow.

The data analysis section 51 receives an input of compressed image datawhich have been compressed and encoded from the input terminal 58 andextracts a target block residual signal, predictive method-relatedinformation, quantization parameters, and motion information (in thecase of inter frame prediction) from the compressed image data. Thecompressed image data contains a residual signal obtained by performingpredictive encoding with the target block resulting from the division ofa single frame image into a plurality of blocks constituting the targetand predictive method-related mode information. The data analysissection 51 outputs the extracted residual signal and quantizationparameters to the reverse quantization section 52 via a line L42 and aline L44 b and outputs motion information and R mode-relatedidentification information and L mode predictive method-related relativeprediction information contained in the mode information to thepredictive method acquisition section 57 via a line L51 and a line L52.In cases where the R mode-related identification information is ‘0’,this indicates that R mode is used as the predictive method and a casewhere the R mode-related identification information is ‘1’ indicatesthat L mode is used as the predictive method. Relative predictioninformation indicates a relative value for the predictive method-relatedinformation in the L mode case.

The reverse quantization section 52 subjects the target block residualsignal to reverse quantization on the basis of the quantizationparameters. The reverse quantization section 52 outputs thereverse-quantized residual signal to the inverse transform section 53via a line L43.

The inverse transform section 53 performs a inverse discrete cosinetransform on the residual signal input from the reverse quantizationsection 52 to restore the regenerated residual signal. The inversetransform section 53 outputs the regenerated residual signal thusrestored to the adder 54 via a line L44.

The predictive signal generation section 55 acquires a reference imagesignal from the frame memory 56 on the basis of the predictive methodderived by the predictive method acquisition section 57 (the details ofwhich will be provided subsequently) and generates a predictive signal.The predictive signal generation section 55 sends the predictive signalto the adder 54 via a line L45 and the adder 54 restores the targetblock pixel signal by combining the regenerated residual signal restoredby the inverse transform section 53 with the predictive signal andstores the target block pixel signal in the frame memory 56 at the sametime as outputting same to the output terminal 59 via a line L48.

The constitution of the predictive method acquisition section 57 will bedescribed next in detail. FIG. 8 is a block diagram which shows theconstitution of the predictive method acquisition section 57. As shownin FIG. 8, the predictive method acquisition section 57 comprises aswitching switch 61, an R mode determination section (first predictivemethod determination means) 64, a storage section 65, an L modedetermination section (first predictive method determination means) 66,and a mode information generation section (predictive method derivingmeans) 67.

The switching switch 61 is a switch which switches the connectionbetween the predictive signal generation section 55 and terminals 62 and63 in accordance with the R mode identification information which isinput via line L51. More specifically, the switching switch 61 connectsto terminal 62 when the identification information is ‘0’ and connectsto terminal 63 when the identification information is ‘1’.

An R mode determination section 64 derives one predictive method on apredetermined evaluation standard for the regenerated adjacent areas, onthe basis of predictive method-related mode information which isdetermined in accordance with the adjacent areas. In other words, the Rmode determination section 64 acquires three or more predictivemethod-related mode information items for previously processed blockswhich are stored in the storage section 65 and determines one predictivemethod by means of a predetermined method. The R mode predictive methoddetermination method is the same as that for the R mode determinationsection 43 of the image predictive encoding device 10. That is, the Rmode determination section 64 determines the predictive method whichcorresponds with the mode information with the highest incidence amongthe intra frame predictive method-related mode information items whichblocks 302 a to 302 f and 303 a to 303 c (see FIG. 3) possess as the Rmode predictive method. The R mode determination section 64 may alsodetermine the R mode predictive method on the basis of the modeinformation of three or more blocks by means of another method. The Rmode determination section 64 sends the R mode predictive method-relatedinformation to the predictive signal generation section 55 via a lineL50 in cases where the switching switch 61 is connected to terminal 62.

The mode information generation section 67 generates optimum predictivemethod-related information in cases where the switching switch 61 isconnected to terminal 63 and L mode is used and sends the optimumpredictive method-related information to the predictive signalgeneration section 55. Thereupon, the mode information generationsection 67 derives information relating to the optimum predictive methodused in the predictive signal generation on the basis of relativeprediction information of predictive method-related information inputvia line L52 and L mode predictive method-related information that isinput from the L mode determination section 66. In other words, the modeinformation generation section 67 generates optimum predictivemethod-related predictive mode information by adding relative predictioninformation relating to the target block predictive method to the L modepredictive method-related information.

The L mode determination section 66 determines the predictive mode fromamong a predetermined plurality of predictive modes for adjacent areaswhich are adjacent to the target block and outputs the predictive modeto the mode information generation section 67 via a line L66 as the Lmode predictive method. The predictive method determination method ofthe L mode determination section 66 is the same as that of the L modedetermination section 46 of the image predictive encoding device 10.

The acquisition processing of the predictive signal generation method ofthe predictive method acquisition section 57 will be described next withreference to FIG. 9. First, R mode identification information extractedfrom the compressed image data are input from the data analysis section51 to the predictive method acquisition section 57 (step S21). Theswitching switch 61 judges whether the information indicates R mode(step S22). In cases where the information indicates R mode (step S22:YES), the R mode determination section 64 determines the R modepredictive method in accordance with the R mode determination method andoutputs the R mode predictive method to the predictive signal generationsection 55 as the optimum predictive mode (step S23). However, in caseswhere the information does not indicate R mode (step S22; NO), relativeprediction information extracted from the compressed image data areinput to the mode information generation section 67 (step S24).Thereafter, the L mode determination section 66 determines the L modepredictive method in accordance with the L mode determination method(step S25). The mode information generation section 67 then determinesthe optimum predictive mode by adding the L mode predictivemethod-related mode information and relative prediction information(step S26). Thereafter, the mode information generation section 67outputs the optimum predictive mode-related information thus determinedto the predictive signal generation section 55 (step S27).

According to the image predictive decoding device 50 describedhereinabove, the R mode and L mode predictive methods are derived forregenerated adjacent areas which are adjacent to the target area whichis the decoding target by using data which have been processed inaccordance with the adjacent areas and the optimum predictive method forthe target area is derived on the basis of the R mode and L modepredictive methods and the relative predictive method, whereby an intraframe predictive signal is generated and this intra frame predictivesignal is used to restore the target area pixel signal from theregenerated residual signal obtained by restoring the target arearesidual signal. The predictive method derived for the adjacent areas byusing data corresponding to the regenerated adjacent areas has a highprobability of being close to the optimum predictive method of thetarget area. Hence, by using this predictive method to restorepredictive method-related mode information of the target area, the bitamount for encoding of the mode information identifying the predictivemethod (relative predictive method) is reduced and the overall decodingefficiency improves.

In particular, in cases where the predictive method is determined on apredetermined evaluation standard by using three or more predictivemethod-related information items which a plurality of adjacent blocksadjacent to the target block each possess as per R mode, there is a highprobability that the predictive method will be close to the originalpredictive method of the target area. Therefore, because this predictivemethod can be taken as the target area predictive method, there is noneed to receive mode information for identifying the predictive method(information identifying nine modes shown in (b) of FIG. 14, forexample). As a result, the transmission amount pertaining to the modeinformation can be reduced by means of simple processing.

Furthermore, in cases where the predictive method which was determinedfrom the nine predictive methods for the areas adjacent to the targetblock is used as per L mode, there is a high correlation to the targetblock predictive method and the target block mode information can bemore efficiently encoded on the basis of the predictive method. As aresult, the effect of reducing the bit amount pertaining to the modeinformation increases. Furthermore, in cases where the areas adjacent tothe target block are subjected to inter frame predictive encoding, evenwhen the adjacent blocks do not have intra frame prediction information,information relating to a predictive method determined from a pluralityof predictive methods for the areas adjacent to the target block or apredictive method which three or more of the adjacent blocks eachpossess is used to determine a predictive method on a predeterminedevaluation standard. Then, the target area prediction information isencoded based on the determined predictive method. As a result, thepredictive method-related information of the target block can be moreefficiently encoded.

An image predictive encoding program and an image predictive decodingprogram which cause a computer to operate as the image predictiveencoding device 10 and the image predictive decoding device 50 will bedescribed hereinbelow.

FIG. 12 shows the hardware constitution of a computer for executing theimage predictive encoding program and image predictive decoding programwhich are recorded on a recording medium and FIG. 13 is a perspectiveview of the computer for executing the image predictive encoding programand the image predictive decoding program stored on the recordingmedium. The computer shown in FIGS. 12 and 13 is not limited to acomputer with a narrow definition such as a personal computer andincludes DVD players, set-top boxes, cellular phones, and so forth whichcomprise a CPU and perform processing and control and so forth by meansof software. A computer 530 comprises a reading device 512 such as afloppy disk drive device, a CD-ROM drive device, or a DVD drive device,a working memory (RAM) 514 where the operating system resides, a memory516 for storing the programs stored on a recording medium 510, a displaydevice 518 such as a display, a mouse 520 and a keyboard 522 which areinput devices, a communication device 524 for sending and receiving dataand so forth, and a CPU 526 for controlling the execution of theprograms. When the recording medium 510 is inserted into the readingdevice 512, the computer 530 is able to access the image predictiveencoding program and the image predictive decoding program which arestored in the recording medium 510 via the reading device 512 and, as aresult of the image predictive encoding program, is able to operate asthe image predictive encoding device 10 of the present invention and, asa result of the image predictive decoding program, as the imagepredictive decoding device 50 of the present invention.

The present invention is not limited to the above embodiments. Forexample, the image predictive encoding device 10 may switch in blockunits between R mode and L mode or the switching may be performed withimage units or sequence units as the switching units. In addition,either R mode or L mode may be employed without performing switching. Inaddition, the R mode determination section 43 and the L modedetermination section 46 in FIG. 2 may also change places or the R modedetermination section 43 and the L mode determination section 46 may beplaced in the same R mode or L mode.

Moreover, although the image predictive decoding device 50 switches inblock units between R mode and L mode, switching may also be performedwith image units or sequence units as the switching units. In addition,either R mode or L mode may also be used without performing switching.In this case, because there is no R mode identification information,either of the functional blocks enclosed by the broken lines in FIG. 8may be employed. In addition, the R mode determination section 64 and Lmode determination section 66 in FIG. 8 may also change places or the Rmode determination section 64 and L mode determination section 66 mayalso be placed in the same R mode or L mode.

In addition, an intra frame predictive signal generation methoddetermination section 115 which is shown in FIG. 10 may be used in placeof the intra frame predictive signal generation method determinationsection 15 shown in FIG. 2 and a predictive method acquisition section157 shown in FIG. 11 may also be used in place of the predictive methodacquisition section 57 which is shown in FIG. 8.

The difference of the intra frame predictive signal generation methoddetermination section 115 shown in FIG. 10 from the intra framepredictive signal generation method determination section 15 entails theprovision of an F mode determination section 143 in place of the R modedetermination section 43. The F mode determination section 143determines the predictive method which arises the most frequently forthe whole frame. More specifically, after storing predictivemethod-related information for each block in the storage section 44 vialine L34, the predictive methods of the respective blocks are read fromthe storage section 44, the majority of the predictive methods among thepredictive methods are derived, and the F mode predictive method isestablished. Here, the predictive mode stored in the storage section 44may also be prediction information relating to a temporally precedingimage or may be a predictive mode relating to the image of the currentprocessing target. The F mode determination section 143 sendsinformation relating to the F mode predictive method thus determined tothe predictive method determination section 41 via line L31.

The difference of the predictive method acquisition section 157 shown inFIG. 11 from the predictive method acquisition section 57 entails theprovision of an F mode information storage section 164 in place of the Rmode determination section 64 and storage section 65. The F modeinformation storage section 164 receives an input of F mode predictivemethod-related information via a line L111 and stores this information.A switching switch 161 switches the connection between terminal 163 onthe mode information generation section 67, terminal 162 on the F modeinformation storage section 164, and the predictive signal generationsection 55 by means of a control signal via line L51. F mode informationstorage section 164 outputs F mode predictive method-related informationto the predictive signal generation section 55 via line L50.

INDUSTRIAL APPLICABILITY

The present invention makes practical use of an image predictionencoding device, an image prediction decoding device, an imageprediction encoding method, an image prediction decoding method, animage prediction encoding program, and an image prediction decodingprogram and permits efficient encoding processing or decoding processingby reducing the predictive method-related mode information forgenerating an intra frame predictive signal in a pixel domain.

1. (canceled) 2: An image prediction encoding device which divides animage into a plurality of areas, generates an intra frame predictivesignal with respect to a pixel signal contained in a target area whichis a processing target among the areas, and encodes a residual signalbetween the pixel signal of the target area and the intra framepredictive signal, the image prediction encoding device comprising:first predictive method determination means which determines, based onprocessed data corresponding to adjacent areas comprising regeneratedpixel signals and adjacent to the target area, a first predictive methodas a predictive method for generating the intra frame predictive signal,wherein the first predictive method determination means derives thefirst predictive method by processing a function including adding orsubtracting of a numerical constant to or from the numerical valuerelating to predictive methods corresponding to the adjacent areas;second predictive method determination means which generates a pluralityof predictive signals corresponding to a predetermined plurality ofpredictive methods for the target area and determines a secondpredictive method which is suitable for the target area from among theplurality of predictive methods in accordance with a predeterminedevaluation standard; predictive signal generation means which generatesthe intra frame predictive signal on the basis of the second predictivemethod determined by the second predictive method determination means;mode information encoding means which relatively encodes the secondpredictive method on the basis of the first predictive method, and imageencoding means which encodes a residual signal of the pixel signal ofthe target area on the basis of the intra frame predictive signalgenerated by the predictive signal generation means. 3: The imageprediction encoding device according to claim 2, wherein the firstpredictive method determination means generates a plurality ofpredictive signals for the adjacent areas corresponding to thepredetermined plurality of predictive methods and determines a firstpredictive method from among the plurality of predictive methods inaccordance with a predetermined evaluation standard. 4: The imageprediction encoding device according to claim 2, wherein the firstpredictive method determination means uses three or more predictivemethods which are previously determined according to the adjacent areasto determine the first predictive method for the adjacent areas inaccordance with a predetermined evaluation standard. 5: An imageprediction decoding device which divides an image into a plurality ofareas, generates an intra frame predictive signal with respect to apixel signal contained in a target area which is a processing targetamong the areas, and restores the pixel signal of the target area bycombining a residual signal relating to the target area contained incompressed image data and the intra frame predictive signal, the imageprediction decoding device comprising: first predictive methoddetermination means which determines, based on processed datacorresponding to adjacent areas comprising regenerated pixel signals andadjacent to the target area, a first predictive method as a predictivemethod for generating the intra frame predictive signal, wherein thefirst predictive method determination means derives the first predictivemethod by processing a function including adding or subtracting of anumerical constant to or from the numerical value relating to predictivemethods corresponding to the adjacent areas; predictive method derivingmeans which extracts a relative predictive method which is relativeinformation identifying the predictive method relating to the targetarea from the compressed image data and derives a second predictivemethod for the target area on the basis of the first predictive methodand the relative predictive method; predictive signal generation meanswhich generates the intra frame predictive signal on the basis of thesecond predictive method derived by the predictive method derivingmeans; restoration means which extracts a residual signal relating tothe target area from the compressed image data to restore a regeneratedresidual signal; and image restoration means which restores the pixelsignal of the target area by combining the intra frame predictive signaland the regenerated residual signal restored by the restoration means.6: The image prediction decoding device according to claim 5, whereinthe first predictive method determination means generates a plurality ofpredictive signals for the adjacent areas corresponding to thepredetermined plurality of predictive methods and determines a firstpredictive method from among the plurality of predictive methods inaccordance with a predetermined evaluation standard. 7: The imageprediction decoding device according to claim 5, wherein the firstpredictive method determination means uses three or more predictivemethods which are previously determined according to the adjacent areasto determine the first predictive method for the adjacent areas inaccordance with a predetermined evaluation standard. 8: An imageprediction encoding method which divides an image into a plurality ofareas, generates an intra frame predictive signal with respect to apixel signal contained in a target area which is a processing targetamong the areas, and encodes a residual signal between the pixel signalof the target area and the intra frame predictive signal, the imageprediction encoding method comprising: a first predictive methoddetermination step in which first predictive method determination meansdetermines, based on processed data corresponding to adjacent areascomprising regenerated pixel signals and adjacent to the target area, afirst predictive method as a predictive method for generating the intraframe predictive signal, wherein the first predictive methoddetermination means derives the first predictive method by processing afunction including adding or subtracting of a numerical constant to orfrom the numerical value relating to predictive methods corresponding tothe adjacent areas; a second predictive method determination step inwhich second predictive method determination means generates a pluralityof predictive signals corresponding to a predetermined plurality ofpredictive methods for the target area and determines a secondpredictive method which is suitable for the target area from among theplurality of predictive methods in accordance with a predeterminedevaluation standard; a predictive signal generation step in whichpredictive signal generation means generates the intra frame predictivesignal on the basis of the second predictive method determined in thesecond predictive method determination step; a mode information encodingstep in which mode information encoding means relatively encodes thesecond predictive method on the basis of the first predictive method;and an image encoding step in which image encoding means encodes aresidual signal of the pixel signal of the target area on the basis ofthe intra frame predictive signal generated by the predictive signalgeneration means. 9: An image prediction decoding method which dividesan image into a plurality of areas, generates an intra frame predictivesignal with respect to a pixel signal contained in a target area whichis a processing target among the areas, and restores the pixel signal ofthe target area by combining a residual signal relating to the targetarea contained in compressed image data and the intra frame predictivesignal, the image prediction decoding method comprising: a firstpredictive method determination step in which first predictive methoddetermination means determines, based on processed data corresponding toadjacent areas comprising regenerated pixel signals and adjacent to thetarget area, a first predictive method as a predictive method forgenerating the intra frame predictive signal, wherein the firstpredictive method determination means derives the first predictivemethod by processing a function including adding or subtracting of anumerical constant to or from the numerical value relating to predictivemethods corresponding to the adjacent areas; a predictive methodderiving step in which predictive method deriving means extracts arelative predictive method which is relative information identifying thepredictive method relating to the target area from the compressed imagedata and derives a second predictive method for the target area on thebasis of the first predictive method and the relative predictive method;a predictive signal generation step in which predictive signalgeneration means generates the intra frame predictive signal on thebasis of the second predictive method derived in the predictive methodderiving step; a restoration step in which restoration means extracts aresidual signal relating to the target area from the compressed imagedata to restore a regenerated residual signal; and an image restorationstep in which image restoration means restores the pixel signal of thetarget area by combining the intra frame predictive signal and theregenerated residual signal restored by the restoration means. 10: Animage prediction encoding program which divides an image into aplurality of areas, generates an intra frame predictive signal withrespect to a pixel signal contained in a target area which is aprocessing target among the areas, and encodes a residual signal betweenthe pixel signal of the target area and the intra frame predictivesignal, the image prediction encoding program causing a computer tofunction as: first predictive method determination means whichdetermines, based on processed data corresponding to adjacent areascomprising regenerated pixel signals and adjacent to the target area, afirst predictive method as a predictive method for generating the intraframe predictive signal, wherein the first predictive methoddetermination means derives the first predictive method by processing afunction including adding or subtracting of a numerical constant to orfrom the numerical value relating to predictive methods corresponding tothe adjacent areas; second predictive method determination means whichgenerates a plurality of predictive signals corresponding to apredetermined plurality of predictive methods for the target area anddetermines a second predictive method which is suitable for the targetarea from among the plurality of predictive methods in accordance with apredetermined evaluation standard; predictive signal generation meanswhich generates the intra frame predictive signal on the basis of thesecond predictive method determined by the second predictive methoddetermination means; mode information encoding means which relativelyencodes the second predictive method on the basis of the firstpredictive method; and image encoding means which encodes a residualsignal of the pixel signal of the target area on the basis of the intraframe predictive signal generated by the predictive signal generationmeans. 11: An image prediction decoding program which divides an imageinto a plurality of areas, generates an intra frame predictive signalwith respect to a pixel signal contained in a target area which is aprocessing target among the areas, and restores the pixel signal of thetarget area by combining a residual signal relating to the target areacontained in compressed image data and the intra frame predictivesignal, the image prediction decoding program causing a computer tofunction as: first predictive method determination means whichdetermines, based on processed data corresponding to adjacent areascomprising regenerated pixel signals and adjacent to the target area, afirst predictive method as a predictive method for generating the intraframe predictive signal, wherein the first predictive methoddetermination means derives the first predictive method by processing afunction including adding or subtracting of a numerical constant to orfrom the numerical value relating to predictive methods corresponding tothe adjacent areas; predictive method deriving means which extracts arelative predictive method which is relative information identifying thepredictive method relating to the target area from the compressed imagedata and derives a second predictive method for the target area on thebasis of the first predictive method and the relative predictive method;predictive signal generation means which generates the intra framepredictive signal on the basis of the second predictive method derivedby the predictive method deriving means; restoration means whichextracts a residual signal relating to the target area from thecompressed image data to restore a regenerated residual signal; andimage restoration means which restores the pixel signal of the targetarea by combining the intra frame predictive signal and the regeneratedresidual signal restored by the restoration means.